Amplifier



p 1941- I l. G. WILSON 2,254,403 I AMPLIFIER Original Filed May 27, 1936 CON TROL IN 5 N TOR 6. WILSON ATTORNEY Patented Sept. 2, 1941 AMPLIFIER lira G. Wilson, New York, N. Y., assig'nor to Bell Telephone Laboratories, York, N. Y., a corporation of New York Incorporated, New

()riginal application May 27, 1936, Serial No.

82,156. Divided and this application September 8, 1988, Serial No. 228,987

3 Claims.

The present invention relates to improvements in amplifiers and more particularly to a power supply for a number of amplifiers such as are operated continuously.

This application is a division of a copending application Serial No. 82,156, filed May 2'7, 1936, for Amplifiers, now U. S. Patent No. 2,191,167, Feb.- 20, 1940.

An object of the invention is the provision of a single battery for use with a large number of amplifiers for both filament lighting and for plate voltage without resulting irregularities in the drain and without undue coupling or crosstalk between amplifiers supplied by the same battery.

Further objects and advantages of this invention will appear from consideration of this specification and accompanying drawing illustrative of a typical embodiment of the invention in which the single figure shows a single power source, used both for filament lighting and for plate current, the full voltage of which is employed for plate voltage and successive sections of which are tapped for filament lighting for separate repeater amplifiers.

The drawing shows schematically a group of amplifiers A, B and C to N, each amplifier being associated with a communication circuit or telephone pair, of which a large number are employed, for example, in a lead covered cable in a carrier telephone system. The circuits may be open-wire pairs, radio circuits or any suitable medium as well as those of a lead covered telephone cable or the like. The amplifier A is associated with one of the circuits or pairs 9 through an input transformer l having suitable shielding. The secondary winding of the transformer I0 is connected in this case to the control grid of a power pentode ll of the type known as 310-A Western Electric pentode tube. The gain of the amplifier is controlled at l2 by some suitable means not shown in detail for varying impedance in shunt of the circuit connecting the input to the output bridge IS. The

tube itself is self-biased by resistance l3 in shunt with a condenser M.

The amplifier A of itself forms no part of the present invention and will not be described in all its details. It is chosen for illustration because it represents a type of repeater to which the power supply circuits of the invention are well adapted. For information as to structure and performance of a'repeater of generally sim- Black U. S. Patent No. 1,956,547, granted May 1, 1934.

The tube II is connected to a succeeding amplifying tube l9 through an interstage network as shown. The plate voltage and the positive screen grid voltage of the tubes II and I9 are fed by the same plate battery 20 through the usual connecting impedance elements from lead 40. The second amplifying tube [9 is connected to an output or power tube 24 through an interstage network similar to that preceding the tube IS. The output or power tube 24 is a 311-A Western Electric power amplifier pentode. The plate of the power amplifying pentode is connected to the positive pole of the plate battery through lead 40 in series with an inductance 25 and through the customry primary winding of the output transformer. The cathode of the power tube is connected to the negative side of the plate supply battery and to ground through an inductance 21. In shunt therewith is a condenser 28 furnishing an alternating current bypass to ground.

The battery 20 employed for both filament lighting and plate voltage supply is a single storage battery of about 150 volts subdivided by taps into n, in this case, seven sections, a, b, 0, etc. The amplifier A has its filaments lighted from section a. The amplifier B has its filaments lighted from section b of the battery and so on while the eighth amplifier at a repeater station has its filaments lighted from the first section a of the battery, the ninth from section b, and

Where the number of amplifiers at a station is less than the number of sections in which the plate battery is divided, or is not an even multiple of such number, individual filament lighting sections not heavily enough loaded may be loaded with dummy loads, such as leak resistances. The drain on the main supply battery 20 is thus kept uniform throughout its length and the usual practice may be followed of keeping the battery on a uniform charge between its end terminals without the necessity for frequent attention to each individual cell to bring it up to normal charge.

It has been noted that the first two tubes of the amplifier are self-biased. A suitable wet or dry biasing C battery 29 is furnished for the power amplifying pentode in ordinary manner.

The power supply system disclosed is not limited in application to telephone repeater service or ilar type, reference may be made to the H. S. to the use Of ei her We or dry battery pp ypole connected to the anodes of said tubes, a heater circuit for the heaters of the first ampli fier connected between the negative pole and an intermediate point in said battery and a heater circuit for another amplifier connectedbetween:

said intermediate point and a more positive poin in said battery. V

2. In a telephone system, a repeater station,.a

plurality of communication circuits at said sta-V.

amplifiers, said power source being tapped to provide a heating current circuit individual to each amplifier.

3. In a telephone system, a repeater station, a plurality of communication circuits at said station, a separate amplifier at said station for each of said circuits, each of said amplifiers including vacuum tubes, a common power source for supplying both anode voltage and cathode .heating current, said source having a negative terminal connected in common to the cathodes of said tubes and a positive terminal connected in common to the anodes of said tubes, a cathode heating circuit for one amplifier connected between the negative terminal and an intermediate point in said source, and another heating circuit for a second amplifier connected between said intermediate point and a more position, an amplifier at said station for each of said circuits, each of said amplifiers embodying vacuum tubes, a single power source for all of said tive point in said source.

IRA G. WILSON. 

